Polymerization of butadiene-1,3 hydrocarbons



Patented July 31,1945 I POLYMEBIZATION F surnames-1,: HYDBOOABBON 8 George L. Browning, Jr., Ahfi: omit-um,

by memo assignments, to Company, Akron, Ohio, a

York

B. F. Goodrich corporation of New No Drawing. Application October 22,1841,

, Serial No. 410,083

8Claims. (c1. zoo-84.5)

This invention relates to the polymerization of butadiene-1,3 hydrocarbons, and particularly to a method whereby butadiene-1,3 hydrocarbons maybe polymerized in the form of aqueous emulsions to form products closely resembling natural crude rubber.

The emulsion polymerization oi 'butadiene-l,3

hydrocarbons either alone or in admixture with other monomers copolymerizable therewith to form compositions of matter more or less resembling rubber is well known. It has been commonly observed, however, that the products of such polymerization reactions often resemble vulcanized rubber rather than natural crude rubber in respect to solubility, plasticity, and processing characteristics. Thus it has often been found that the polymers were insoluble in, and, in some cases, not even swelled by benzene or-acetone, and that they were tough, non-plastic materials which either would not homogenize on a mill or which were very diificult to mill and to subject to other ordinary processing operations.

I have now discovered a class of materials which modifies the emulsion polymerization of' butadiene-l,3 hydrocarbons in such a manner that polymers more nearly resembling natural crude rubber may be produced than when the polymerization is effected in the absence of the materials of this invention. The class 0! materials, which I have termed modifiers, consists 1 of compounds containing the group a-x-c :s-czN wherein R is an organic radical derived by removing tire hydroxyl group from a monohydric alcohol and X represents oxygen or sulfur. These compounds may be prepared by reacting an alkali metal xanthate or thioxanthate with a cyanogen halide with the elimination of salt. Sodium isopropyl xanthate, for instance, may be reacted with cyanogen chloride with the elimination of sodium chloride to form isopropoxythiono cyano monosulfide according to the 'iollowlng equation:

The reaction may conveniently be effected by settles to the bottom as an oil. If desired, an organic solvent such as acetone may be used in place or water.

The xanthates employed in this reaction may be prepared by the known reaction with carbon disulfide and an alkali such as sodium hydroxide of an alcohol such as methyl alcohol, ethyl alcohol,

- iscpropy alcohol, ten-brityl alcohol, act. amyl alcohol, lauryl alcohol, benzyl alcohol, cyclohexyl alcohol, tetrahydroiuriuryl alcohol, allyl alcohol.

- methoxy-ethyl alcohol, or one of the corresponding thiols.

The efi'ect of the modifiers oi this invention on emulsion polymerization is shown by the copolymerization at C. of 55 parts by weight of butadiene-LS and 45 parts of acrylonitrile in.

the presence oi. about. 250 parts or a 2% aqueous solution or myristic acid which had been 85% neutralized with sodium hydroxide, 0.35 part of hydrogen peroxide as an initiator, 0.11 part of sodium ierri pyrophosphate as an activator. and

0.35 part of isopropoxythiono cyano monosulfide. The polymer obtained by coagulating the latex formed was in a plastic and coherent form and was 35% soluble in acetone, while the polymer obtained by polymerization in the absence of any modifier was in the form of non-coherent crumbs which were practically insoluble in acetone. The vulcanizate prepared by testing the modifier in a tire tread recipe was unusually strong and exhibited a high elongation. y

The proportion in which the modifier is included in the composition depends somewhat upon the properties desired in the product, the higher proportions of modifier in general producing softer, more soluble polymers. Very small amounts of modifier such as 0.1% or even less based on the monomers in the emulsion may proioundly affect the nature of the polymer produced, and amounts up to 5% or more may advantageously be employed. It may also be advantageous to employ a mixture of one of the modifiers herein claimed with other known types of modifiers such as tetraalkyl thiuram polysulndes, mercaptoalkylthiazoles or other types oi compounds known to exhibit modifyin a tivity in emulsion polymerization pr.

The modiiyins agents of this invention may be employed in the polymerization in the'torm of an aqueous emulsion oi'butadiene-Lii hydrocarbons, by which is meant butadiene-L3 (commonly termed butadiene) and its homologues which enter into polymerization reactions in essentially the same manner, either alone or in admixture with each other and/or other monoisobutylene, acrylonitrile, methyl methacrylate,

methyl acrylate, methyl vinyl ether, methyl isopropenyl ketone, and other unsaturated hydrocarbons, esters, ethers, and ltetones. For the production of rubbery products, these other monomers should be employed in an amount smaller than the butadiene.

c The polymerization of the above materials in aqueous emulsion may be effected by various in,

. itiators ofpolymerization such as per-compounds including per-acids, peroxides, and perv-salts such as persulfates, perborates, perc'arbonates, and the like as well as other types of initiators such as diazoaminobenzene, hydrosulfltes, bisuliites. and

dipotassium diazomethane disulfonate.

The polymerization reactions may be catalyzed in any desired manner, the use of heavy metal catalysts being particularly desirable. The heavy metal catalyst may be added tothe emulsion in the form of less than 0.1% based on the weight of the monomers of a simple ionizable heavy metal salt such as cobalt chloride, nickelous sulfate, mercuric chloride, etc., as disclosed in the copending application of William D. Stewart,

, mers copolymerizable therewith such as styrene,

wherein R is an organic by removing the hydroxyl group from a monohydrlc in aqueous emulsion a mixture of butadlene-1,3

Serial No. 379,712-flled February 14, 1941 or in 'the form of a redox system comprising a heavy metal and a material such as sodium pyrophosphate, levulinic acid, glycine, cystine, beta-mercaptoethanol, quebrachitol. ox-bile or chloresterol as disclosed in the copending'applications of William D. Stewart, Serial Nos. 379,713 to 379,717 filed February 14, 1941.

Any of the ordinary emulsifying agents such as fatty acid soaps including sodium oleate, potassium stearate, sodium myristate, etc., may be employed, as well as synthetic'saponaceous materials such as hymolal sulfates and alkaryl sulfonates including sodium lauryl sulfate and sodium isopropyl naphthalene sulfonate.

Although I have herein disclosed specific embodiments of my invention, I do not intend to limit the invention solely thereto, for it will be obvious to those skilled in the art that many variations and modifications are within the spirit and scope of the invention as defined in the appended claims.

I claim:

1. The method which comprises polymerizing a butadiene-1,3 hydrocarbon in the form of an aqueous emulsion in the presence of a small amount of a compound of the formula and a smaller amount of a mono-oleilnic monomer copolymerizable therewith in aqueous emulsion, in the presence of a small amount of a compound of the formula R-l-C-B -CEN wherein R is an organic radical derived by removing the hydroxyl group from a monohydric alcohol and X is a member of the group consisting of oxygen and sulfur.

5. The method which comprises polymerizing in aqueous emulsion a mixture of butadiene-LS" and a smaller amount of a mono-oleflnic monomer copolymerizable therewith in aqueous emu1 sion, in the presence of an alkoxythiono cyano monosulfide wherein the alkoxythiono and cyano groups are directly attached to the same sulfur atom.

6. The method which comprises polymerizing in aqueous emulsion a mixture of butadiene-Lt and a smaller amount of a mono-olefinic monomer copolymerizable therewith in aqueous emulsion, in the presence of isopropoxythiono cyano monosulflde.

7. The method, which comprises polymerizing a mixture of butadiene-1,3 and a smaller amount of acrylonitrile in aqueous emulsion in the presence of isopropoxythiono cyano monosulfide.

8. The method which comprises polymerizing a mixture of butadlene-L3 and a lesser amount of styrene in an aqueous emulsion in the presence of isopropoxythiono cyano monosulflde.

(moms L. BROWNING, Jn. 

